Radio receiving system



Mar. 6, 1923. 1,447,793

M. LATOUR RADIO RECEIVING SYSTEM 2 sheets-sheet 1 Filed Aug. 19, 1921 amvem coz MAPJUS LATOUR M. 'LATOUR RADIO RECEIVING SYSTEM Filed Aug. 19, 1921 2 sheetssheet 2 IAAAAAAIIAA In"! awumtoz MMUUS LATQUR 3W iimw HARRIS maroon, or rears, rcn.

RADIO RECEIVING SYSTEM.

Application filed August 19, 1921. Serial R'o. 493,660.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L, 1313.)

1920), of which the following is a specification, accompanied by drawings.

The resent invention relates to improvements 1n circu t arrangements of radiotelegraphic receiving stations for the purpose of increasing the sensitiveness of the receiving and making possible the application of the princi le of heterodyne action in the reception of ertzian waves.

As well known, in the case of crystal detectors, the rectified portion of the current is proportional to the square of the alternating potential n acting on the circuit comprising the detector. On the otherhand, if a potential V of a slightly different period is introduced into the receiving circuit, it is found that the sensitiveness of the receiving increased with the potential V up to a certain limit.

It has been ,found advisable to increase V until the law oi the square no longer holds good and up to a point beginning at which the rectified portion of the current is simply proportional to the potential a plied to the detector. The increasing of V value will be useless.

The only dificulty that will be encountered in increasing V will be the presence of a ermanent rectified current in the telephone. his permanent'current will cause the permanent attraction. of the diaphragm that may cause a lowering of the sensitiveness of the telephone. As a result of this, beginning With a certain value for V, the increase'in sensitiveness corresponding to the increase of V will beconcealed.

This disadvantage may be remedied in the following simple manner:

'A simple expedient is to use telephones provided with magnets of lower magnetization. The permanent rectified current would only add its efiect to the magnetism of the magnet to supplement its insufiiciency and produce the necessary ermanent induction under the diaphragm. t is also conceivable that we may operate without a permanent magnet and. use only the rectified current above this for producing the necessary permanent induction.

In the drawings, Fig. 1 showsthe general arrangement of the telephone to be used, Fig. 2 shows a circuit for receiving with a crystal detector, Figs. 3, 4, 5 and 6 show arrangements with two detectors, and Fig. 7 shows a circuit arrangement in which a mercury rectifier is used.

The general arrangement of the telephone to be used is shown in Fig. 1 in which represents the vibrating diaphragm, F the magnetic core and B the coil of the telephone.

The telephone is energized by means of a current of the proper continuous potential and direction passing through the telephone coil B. This continuous potential is obtained in the usual manner at the terminals of a 'potentiometer'R supplied with current from a battery E. The self induction coil Z is inserted for the purpose of preventing the passage of the telephonic current through this branch lhe direct current source may produce a current of the same direction as the rectified current, or even current of the opposite direction.

The direct current source may or may not be connected with the detector depending whether or not the latter is protected by a capacity C in seriesl If there is no objection against new losses, 2. simple transformer may be used.

In this manner, the passage of the permanent rectified current through the telephone circuit will be prevented and the J ordinary telephone action will-be preserved.

As above stated, beginning with a certain value of V, it is impossible to increase the sensitiveness of the heterodyne. A. method will be explained which makes possibl a further increase of this sensitiveness after the increase of V becomes inefiicacious.

The circuit shown in Fig. 2 is used for receiving with crystal detectors and contains one embodiment of the invention. 1L represents the secondary inductance of the receiving circuit. with the telephone T is connected in parallel with the condenser C. An additional condenser C is connected in parallel with the telephone T. No matter what may be said of the operation of a crystal detector, apparently it rectifies part of the alternating The'deteotor D in series 4 current by which it is traversed. Whether this is caused by the eiiective rectification of the alternating current or the appearance of a continuous E. M. F. of thermoelectric origin, is without consequence on the phenomenon in the shunt DT. Under all circumstances the conclusions would be the same.

The crystal detector acts actually only as animperfect rectifier, but we may nevertheless consider it as a perfect rectifier for a certain portion of the alternating current, the only portion that affects the receiving. The non-rectified portion corresponds to an alternating current which passes without useful effect at least through the general inductance and the capacity of the receiv- 1n circuit.

imiting ourselves to the rectified portion of the current, it should be remembered that only one-half a wave of the alternating current is utilized in the telephone circuit, the other half being suppressed. Notwithstanding this, one might conclude from the reasoning that is to follow that, the Quantity of the rectified electricity may be educted from two successive half waves.

Referring to Fig. 2, as long as the direction of the current in the general circuit is such that it may pass through the detector D, it will pass through L, D and T, and the condenser C will receive only a weak charge. When the direction of the current is reversed, the condenser will on the contrary receive a strong charge, and it might happen that the quantity of the electricity thus stored be added by the discharge of the condenser through DT to the electricity efi'ectively rectified during the following half period.

Nevertheless, in such reasoning it must not be overlooked that the two waves of the oscillating current cannot be equally absorbed, and that a current having symmetrical waves is out of the question in the receiving circuit. As a matter of fact, the condenser C can under no circumstances take other than alternating current transportin equal quantities of electripg tly of both dlrections and that the circuit absorbs only direct current.

The sum of these two currents will therefore never be an alternating current that transports equal quantities of electricity of both directions and there can be no question of a useful sine wave current in the receiving circuit and of supplying ener for each half wave. However, a perfect y symmetrical arrangement may be realized by using two detectors- This is shown in the following Fig. 3 shows an arrangement in which two detectors D and D are connected in the opposite direction with respect to the main circuit comprising inductance L and capacity C. T and'l are two telephone P and simultaneously acting on a single.

secondary winding S, as shown in Fig. 4.

The arrangement with two detectors shown in Figs. 3 and 4 may have the form of Figs. 5 and 6. In Fig. 5 detectors D and D connected in opposite directions, are respectively in parallel with T C and T 0' In Fig. 6 a transformer is provided with two primary windings P P and a secondary S and the other reference characters desigmate the same elements as in Figs. 3 and 4.

The circuit arrangement shown in Fig. 7 also may be ,used. In this arran ement a mercury rectifier is used, the self induction of the antenna being employed as an auto transformer.

If the circuit arrangements of'Figs. 3, 4,

5, 6 and 7 are combined with the meet the heterodyne, consisting in the introduction of an E. M. RV and an auxiliary E. M. F. V in the main circuit and if a sufficiently large auxiliary E. M. F. V is used so that the rectified portion of the current be in roportion with the potential applied to the two detectors, twice as sensitive a reccivin circuit may be obtained as in case the usua quantities are used.

Having described my invention, what I claim is:

1. In a radio signaling system, the combination with a detector and a telephone of a heterodyne receiver connected thereto having the auxiliary E. M. F. ofthe heterodyne adjusted to a high value whereby a permanent rectified current component results in the telephone, means for magnetizing the magnet of said telephone and means for varying said magnetization, said means being adjusted to a point such that the resultant magnetization due to said rectified current and said magnetizing means maintains the sensitiveness of the telephone.

2. In a radio signaling system, the combination of a heterodyne receiver, a pair of rectifiers adapted to rectify currents from opposite directions, a coil associated with each detector and indicating means associated with said coils.

3. In a radio signaling system, the combination of a heterodyne receiver, a pair of rectifiers adapted to rectify currents from opposite directions, a 'coilassociated with each detector, indicating means associated with said coils anda condenser in parallel thereto.

4. .In a radio signaling system, the combination of a heterodyne receiver, a pair of oppositely connected rectifiers connected to said receiver and a telephone connected to each detector and. to the receiver.

5. In a radio signaling system, the combination of a heterodyne receiver, a pair of oppositely connected rectifiersconnected to said receiver and a telephone connected to each detector and to the receiver, and a capacity in said receiver connected in parallel to a detector and telephone.

6. In a radio signaling system, the combination-of a heterodyne receiver, a pair of rectifiers connected thereto and inparallel to each other adapted to rectify currents from opposite directions, a coil connected to each detector'and a telephone circuit coupled to each of said coils.

7. In a radio signaling system, the combination of a heterodyne receiver, a pair of rectifiers connected thereto and in series with each other with the opposite poles connected together a coil connected in parallel with each rectifier and indicating means associated with each of said coils.

8. In a radio signaling system, the combination of a heterodyne receiver, a coil associated with said receiver, a telephone connected to an intermediate point of said coil in parallel with a pair of rectifiers connected to opposite sides of said coil.

IUS LATO. 

